The present invention relates to a crosstalk cancelling circuit for removing a crosstalk component introduced into a reproduced signal of a video tape recorder (VTR).
In VTRs, to remove a crosstalk component due to the adjacent track, a crosstalk cancelling circuit based upon the so-called PS (Phase Shift) system is known, an example of which is illustrated in FIG. 1. In FIG. 1, to an input terminal 1 is supplied a frequency-lowered conversion chrominance signal (frequency down-converted chrominance signal) of 629 KHz (=40f.sub.H :f.sub.H represents a horizontal synchronizing frequency) reproduced from a magnetic tape. To an input terminal 2 is fed a local oscillating signal of 4.2 MHz generated by a local oscillator. In order to perform the crosstalk cancellation in accordance with the PS system, the phase of the frequency-lowered conversion chrominance signal is rotated by .+-.90.degree. at every 1H (1H is one horizontal scanning period on the occasion of recording). The rotating direction differs at every adjacent track, and if the rotating direction is positive with respect to one track, the rotating direction is changed to be negative with respect to the tracks adjacent thereto. The phase of the local oscillating signal supplied to the terminal 2 is rotated by .+-.90.degree. at every 1H in the same directions as the phase rotation directions of the recording frequency-lowered conversion chrominance signal.
The aforementioned two signals are inputted into a multiplier 3 for multiplication which in turn causes frequency conversion. Thereafter, a band-pass filter (BPF) 4 produces a signal whose central frequency is 3.58 MHz (4.2 MHz-629 KHz). The output of the BPF 4 is directly inputted into a subtracter 6 and further supplied thereto after passed through a 1H delay device (1HDL) 5. In the subtracter 6, the crosstalk component is cancelled by subtraction between the inputted two signals and a signal resulting from the subtraction is outputted as a carrier chrominance signal.
The conventional circuit of FIG. 1 is arranged such that the frequency-lowered conversion chrominance signal (629 KHz) is frequency-converted so as to have a frequency of 3.58 MHz before cancelling the crosstalk. Thus, when a glass delay device is used as the 1HDL 5, difficulty is encountered in machining to obtain high accuracy due to the frequency being high. Further, in the case of use of a charge coupled device (CCD), since the passing band is high, a number of steps are required (generally, 680 steps or 910 steps), resulting in disadvantage in cost.